1. Field of the Invention
Present invention is directed to a method and apparatus for transferring a pre-molded film into a mold. More specifically, the present invention is directed to providing a robotically controlled moveable arm to transfer a flexible, pre-molded film into an injection-molding tool.
2. Description of the Related Arts
It is known to manufacture injection molded articles in an injection molding press. Generally, the robotically controlled arm manipulates a device called an unloader to remove articles manufactured in the press. The unloader secures the molded article by vacuum and lifts the molded article from the core portion of the mold.
It is also known to manufacture molded articles using flexible films wherein the film is placed within a mold cavity and a polymer is injected behind the film to heat and soften the film backing. The film backing fuses to the polymer to form a molded article. An example of this type of method is taught in U.S. Pat. No. 3,668,034. One difficulty in manufacturing molded articles using pre-molded flexible films, is properly positioning the flexible film within the molds so that it is free of wrinkles or creases and is precisely positioned in the cavity to register with the cavity contours to form the desired article. Heretofore, proper placement of the pre-molded film within the cavity has been a major stumbling block to widespread application of pre-molded films. The problem is especially acute when handling thin pre-molded films for large automotive applications such as bumper facias, instrument panels and door panels. The entire surface area of the film must be properly positioned within the cavity to produce a defect-free article. Slight misalignments will cause wrinkles or defects and make the article unusable.
It is necessary to precisely place the film between the operable core and cavity pieces of a molding press. Because these operable pieces open and close, it is advantageous to provide a mechanism which allows the pre-molded film to be robotically placed within the mold rather then manual placement by an operator. It is a further desired result of the present invention to utilize the existing equipment for removing the molded article from the core, in the method for placing the pre-molded film within the mold. It is also desired that the method and apparatus utilize existing molding equipment to the maximum extent possible. This includes utilizing a mold press and core with a limited opening there between. It is further desirable to manufacture an article in a tool that is subject to "die-lock" conditions. Die-lock conditions occur when the molded article has a dimension greater than the opening of the mold. Die-lock prevents the article from being removed from the cavity after the molding operation. Utilizing die-lock conditions enables the manufacture of parts with covered edge portions or flanges.
A variety of methods are known for removing articles from molds that are subject to die-lock, however, a method of placing flexible films within a cavity that is subject to die-lock has not been shown. It is yet another desired object of the present invention to provide a method and apparatus for placing a pre-molded film into a cavity that is subject to die-lock conditions. It is further desirable to precisely position a pre-molded film within a cavity so that edge portions are placed within the cavity and a flange portion is formed behind the edge portion.
It is known to form a covered edge using in-mold films. An example of this construction is illustrated in U.S. Pat. No. 5,599,608. A film having a re-entrant edge portion is placed within a mold. A cavity is moved to contact the core. The core engages the re-entrant portions and folds them within the cavity. Molten plastic is injected into the cavity and the combination of closing the mold combined with the pressure the molten plastic material forces the re-entrant edge portions against the cavity wall to form the covered edge of the molded article. The method described in U.S. Pat. No. 5,599,608 is limited to forming an edge portion having a width equal to the thickness of the substrate. This is useful when forming a part having a covered edge, but not useful when forming a part having a covered flange portion. A flange creates a space behind the flange known as an undercut. The U.S. Pat. No. 5,599,609 patent does not teach forming parts having an undercut.
These deficiencies and problems are overcome by the present invention.